In the production of standard grades of paper on a conventional paper machine, cellulose fibers and water are combined in a headbox to form an aqueous fiber furnish. A wet fibrous web is then formed on the papermaking wire, and the water is mechanically removed from the web. This mechanical dewatering step increases the consistency of the web from about 5%, the consistency on formation, up to about 40%, or more. As the water is mechanically displaced from the web, the fibers forming the web are moved into close proximity with each other. Chemical papermaking bonds, generally described as hydrogen bonds, are formed between adjacent surfaces of a substantial number of the cellulose fibers. The formation of these hydrogen bonds serves to strengthen the web, as measured, for example, by a substantial increase in the physical strength properties of the web.
The uncontroled formation of substantial numbers of hydrogen bonds between the surfaces of adjacent fibers is, however, detrimental to paper properties such as absorbency, bulk and softness which are critical in certain grades of tissue and towel. Therefore, conventional papermaking, as described above, cannot readily be employed in this latter application where high quality products are described.
In an attempt to upgrade conventionally formed paper and to produce a paper product having increased absorbency, bulk, and softness properties, certain prior art methods treat cellulose with chemical "debonding agents". For instance, U.S. Pat. Nos. 3,812,000 to Salvucci et al; 3,844,880 to Meisel et al.; and 3,903,342 to Roberts et al., respectively, as well as pending applications U.S. Ser. Nos. 99,041 and 176,225, assigned to the assignee of the present invention, describe improving the softness of cellulose employing various debonding agents. Typical debonding agents used are fatty, long-chain amine compounds. The most effective of these materials are the cationic compounds typified by quaternary amines such as described in Hervey et al., U.S. Pat. Nos. 3,554,862; 3,554,863; and 3,395,708.
The above described effect in paper is quite different from, for example, the "softening" effect in textile fibers. In the case of textiles, the surface is made soft to the touch and is, in essence, "lubricated". However, these textiles maintain a very high level of internal strength since this is a requirement of textile fabrics. Neither bulk nor absorbency of the textiles is substantially increased. The softening effect is contrary to the effect in the previously described high absorbency and bulk applications wherein the mechanical strength properties of the sheet are modified. Patents such as U.S. Pat. Nos. 3,104,935 to Moyse; 3,124,414 to Dolmetsch; 3,057,675 to Hiestand; and 3,847,915 and 3,961,892 to Bishop et al. describe the use of various 1,3,5-triazine ring materials as softening compounds for textile materials. In an article in the 1971 Australian Journal of Chemistry, Volume 24, pages 26, 49-54, the preparation of triazinyl compound, i.e., bis(dichlorotriazinyl) derivatives of diethylene and triethylene glycol, for application to wool, is described by Ayscough et al.
The reaction of cyanuric chloride with cellulose has also been described in U.S. Pat. Nos. 1,886,480 to Haller et al.; 2,892,674 to Sause; 4,035,146 to Brenner et al.; and various journal articles including "Action of Cyanuric Chloride on Cotton Cellulose", by Warren et al., in Textile Research Journal, September 1952; and a series of articles by Allan et al., including "Fiber Surface Modification, Part IV. The Reactivity of Lignocellulosic Fibers with Cyanuric Chloride", in Volume 53, No. 8, of TAPPI, August 1970; and "Fiber Surface Modification. Part XIII. Constitutive Fiber Parameters for the Reaction of Pulps with Cyanuric Chloride", in Specialnummer 4a, Papper och Tra (1972).
British Pat. No. 1,131, 762 to Colgate-Palmolive Company is directed to the use of large amounts, i.e., 5% to 50%, of a poly(ethylene oxide) compound having an average molecular weight in the range of 280 to 810 as an internal plasticizer.
Other softening agents for fibers include an emulsion of chlorocyanuric acid and a fatty acid. This emulsion is used for cotton and rayon fibers and is described in Japanese Pat. No. 74-40,035.